I was at a coaches clinic when the head coach of Mich St commented that she was shocked when she attended a HS game that ended 1-0 because according to the profiles she receives, every kid in HS bats between .600 and .750.
If someone has to recite stats to tell you how great their daughter is, then she's probably mediocre at best. If DD really hits .750 you should only have to watch a few at bats to see how good they are.
I do think there are plenty of HS kids hitting .600-.750. What happens is that the better ones are playing up an age bracket (or two) and are facing good Varsity level pitching by 13 (sometines even younger). By the time they are seniors this is their 4th or 5th year hitting against the same level of pitching and they can dominate offensively. As you would expect their batting average will drop when they go to college (and face consistantly better pitching) and I am sure the same happens to pitchers who had low ERA's in HS that get higher when facing collegiate batters who are more consistantly solid.